New approach in the study of hydrogen dynamics in metal hydrides by neutron transmission experiments

We propose a new approach to the analysis of total cross-section measuremen ts of hydrogen in metal hydrides, aimed at obtaining primary information ab out the dynamics of hydrogen in these compounds, including the characterist ic frequencies and mean-square displacement of the proton. We use a simplif ied model to describe the hydrogen vibrational spectra and a translational effective mass to take into account the hydrogen diffusive motion. This app roach is based on the splitting of the total incoherent cross-section in tw o well-defined terms: a quasi-elastic contribution - depending on the trans lational effective mass and the mean-square displacement of hydrogen atoms - and an inelastic contribution, related to the vibrational frequency spect ra. In this work we present the starting approximations and develop the for malism involved in the analysis, illustrating its application through exper iments performed on zircaloy-4, magnesium and niobium hydrides. (C) 1999 El sevier Science B.V. All rights reserved.